The invention applies in particular to the production of argon by means of air distillation plants having a double distillation column.
In such a plant with a double air distillation column, medium-pressure nitrogen is generally removed from the top of the medium-pressure column of the double column. This medium-pressure nitrogen is generally used, after expansion in a turbine, as a source of refrigeration, especially to cool the air to be distilled. Thus, a portion of the refrigeration energy supplied to the air to be distilled can be recovered and therefore the operating costs of such a plant can be reduced.
Such a plant is designed to meet nominal argon production requirements with a nominal argon extraction yield .rho..sub.n at the outlet of the impure-argon production column, called the mixture column. In general, it is sought to have a maximum yield .rho..sub.n.
Hitherto, when the argon production requirements decrease, for example during periods of less load on a consuming plant or when storage tanks to be filled are full, the argon extraction yield .rho. at the outlet of the impure-argon production column is correspondingly reduced in order to meet at the very most these reduced argon-proauction requirements.